FIELD OF THE INVENTION
The invention relates to nuclear power generation, and more specifically it pertains to an apparatus for inerting and venting the atmosphere of a containment vessel in a nuclear power station, and to a method for operating an apparatus of this type.
In the event of an emergency or an accident in a nuclear power station, where, for example upon the oxidation of zirconium when the core is heated, the formation and release of hydrogen gas within the safety vessel or containment surrounding the reactor core must be expected. Explosive gas mixtures may form as a result within the containment.
In order to prevent explosive gas mixtures of this type from being formed in the containment of a nuclear power station, various devices or methods are envisioned. These include, for example, devices, such as catalytic recombinators, catalytically and electrically operated ignition devices, or the combination of the two systems, as well as methods for permanent or subsequent inerting of the containment.
In order to inert the containment of a nuclear power station, a nonreactive gas, such as, for example, nitrogen (N.sub.2) or carbon dioxide (CO.sub.2), may be supplied as an inerting agent into the containment. In an alternative process, liquid gas may be fed in for inerting via branched nozzle systems or conventional gas feed systems with an integrated oil burner or gas burner evaporator plant. Other variants are based on a feed of liquid gas, a feed into a water sump within the containment also being provided on account of the absence of evaporation energy in the atmosphere of the latter. An apparatus for inerting the atmosphere in the containment of a nuclear power station is known, for example, from German patent specification DE 44 21 601 C1.
Feeding an inerting agent into the containment may result in a pressure rise within the containment. Such a pressure rise may also occur in an already preinertized containment, in particular one with a high specific Zr mass and small containment volume. This in turn makes it necessary to relieve the containment pressure by venting the containment atmosphere. However, the containment atmosphere usually contains radioactive material, such as, for example, inert gases, iodine or aerosol, which could escape into the surroundings of the nuclear power station during venting. Accordingly, because of the radioactive material in the containment atmosphere, venting of the containment atmosphere in the event of an accident or fault does not come under consideration.